| 摘要 |
A magnetic ink concentrate is described which consists essentially of a dispersion of magnetically hard solid particles in water or alcohol in the presence of polyelectrolytes having a molecular weight of between 1000 and 25,000 and selected from the group consisting of polyacrylates, acrylic acid-acrylamide copolymers and polyvinylphosphonic acids and the alkali metal salts of these compounds, with the proviso that the magnetic pigments have a specific surface area of from 70 to 200 m<2>/g, a coercive force of between 10 and 500 kA/m and a residual induction of more than 10 nTm<3>/g. The polyelectrolytes used may also be biodegradable polycondensates (polycondensation products) of organic hydroxycarboxylic acids, alcohols or acetals. The magnetic ink concentrate can be very easily prepared in one operation. |
